The conventional fluorescent lamp lighting circuits include a starting lamp type, a rapid starting type and an electronic type. The fluorescent lamp used in such lighting circuits is superior over the incandescent lamp, because the fluorescent lamp has a higher light emitting efficiency and a longer life expectancy than the incandescent lamp. However, a starting time for lighting the fluorescent lamp is lengthy. If the fluorescent lamp is operated to repeatedly blink, its life is greatly decreased. For this reason, fluorescent lamps could not be used for the case where the lamps continuously blink as in an advertising panel.
Further, a fluorescent lamp is greatly influenced by various external factors such as the lighting circuit, the performance of the starting switch(grow starter) and the ambient temperature. Consequently, the light flux are easily decreased, and the starting ability is easily degraded.
Further, during the lighting of the lamp, the starting voltage alteration and the fluctuation of the current act as impact pulses to the filament, thus resulting in a decrease of the light emission and the formation of dark specks. Accordingly the life expectancy of a fluorescent lamp largely depends on the number of lighting manipulations.
Korean Utility Model Publication No. 90-2834 (issued Apr. 4, 1990) discloses an attempt to overcome the above described disadvantages of the conventional fluorescent lamp lighting circuits. In this publication, if a fluorescent lamp is used as an ordinary illuminating means, lighting is started with a blocking oscillation voltage by using a DC power source without using a grow starter lamp, and a small AC voltage is applied to the fluorescent lamp heater so that the heater may not be damaged. In the case where the fluorescent lamp is used as an automatically blinking lamp, a low AC voltage is applied to the lamp heater all the time, thereby preventing the shortening of the fluorescent lamp life expectancy and the occurrence of dark specks. Thus a low voltage is applied to the lamp heater by an AC transformer all the time in order to prevent the damage of the heater. This reduces shortening of the life of a fluorescent lamp that would otherwise be caused by the damage of the heater during the lighting of the lamp. Therefore, a low AC voltage is made to be induced on the heater during the lighting of the lamp, and the polarity of the heater is continuously changed, thereby protecting the heater and extending the life expectancy of the heater.
However, the lighting circuit proposed by Korean Utility Model Publication No. 90-2834 has many problems in applying it to the practical use.
First, a power of 60 Hz is continuously supplied to the heater during the operation, and therefore, the power loss is very large. Further, the operating temperature of the fluorescent lamp is elevated, and this brings adverse effects such as the decrease of the light emitting efficiency and the shortening of the life expectancy.
Second, a flickering phenomenon inevitably occurs due to the connection characteristics of the oscillating circuit and the choke coil.
Third, the initiating current has to be very large, and therefore, the initiation becomes very unstable, as well as shortening the life expectancy.
Fourth, even during the time when the automatic blinking is not carried out, the AC power source continuously supplies the triggering pulses, with the result that the transistor connected to it is degraded and apt to malfunction.